FIG. 1 depicts a portion of a conventional ultrasonic handpiece 10 usable in ophthalmic surgery. The ultrasonic handpiece 10 includes a housing 12 and a horn 20 which vibrates ultrasonically in the housing 12. The housing 12 includes an irrigation line 14, a channel 16 and a chamber 18 through which fluid may flow. The irrigation line 14 runs along the axis of the handpiece 10 and may be formed of a separate component. The chamber 18 is centrally located. The horn 20 extends through the chamber 18. The horn 20 may be oscillated, for example using piezoelectric crystals (not shown). O-ring 19 isolates the chamber 18 from the remainder of the ultrasonic handpiece 10.
The ultrasonic handpiece 10 allows for fluid flow through the eye during ophthalmic surgery. During such a procedure, the tip attached to the ultrasonic handpiece 10 is inserted through an incision in the eye. Fluid is driven through the irrigation line 14, to the channel 16 and into the chamber 18. The direction of fluid flow is shown by arrows in FIG. 1. The fluid travels out of the chamber 18 into the eye near the tip of the horn 20. The fluid may be used to remove cataractous lenses from the eye utilizing a surgical technique called Phacoemulsification.
Although the conventional ultrasonic handpiece 10 functions, there are drawbacks. The interior of the eye is desired to be kept stable during the ophthalmic procedure. Disturbances in the fluid flow from the handpiece 10 into the eye are undesirable. One such disturbance may be caused by bubbles in the fluid. When these bubbles enter the eye, the bubbles could cause fluctuations in the intra ocular pressure in the eye and can lead to instability in the anterior chamber of the eye. The bubbles may also adversely affect visualization of the operating field. To reduce or eliminate the bubbles, the operator hand primes the ultrasonic handpiece 10. Priming the handpiece 10 includes orienting the ultrasonic handpiece 10 so that the horn 20 is vertical (ninety degrees counterclockwise from the orientation shown in FIG. 1) and tapping the ultrasonic handpiece 10 while fluid is flowing through the chamber 18. Failure of the operator to prime the handpiece 10 may result in the flow disturbances described above. The manufacturer of the ultrasonic handpiece 10 is unable to guarantee that the operator correctly primes the ultrasonic handpiece 10 each time the handpiece 10 is used. For the above reasons, it may be challenging to ensure that the ultrasonic handpiece 10 provides uniform intra ocular pressure.